Green District Heating and Cooling (DHC) is a Key Component of a Decarbonized World
As the world awakens to the urgency of reducing carbon emissions, governments are setting enforceable targets to ensure those reductions are achieved. Delivering zero carbon heating and cooling across the world is one of the keys to meeting these decarbonization objectives. Consequently, introducing Green DHC is an important element of a sustainable solution, one that particularly makes sense for city districts, industrial and commercial parks, campuses and airports as they strive to meet the emissions goals of tomorrow. And while decarbonization solutions such as Green DHC often seem costly and complex, with the right expertise and an innovative mindset, it is entirely possible to unlock its great potential.
Global warming is the most critical challenge of our time, and cities have a key role to play in driving the transition to a low-carbon economy. The City of Helsinki recognizes the need to make significant changes to facilitate the transition to a sustainable future and has set itself an ambitious goal: becoming carbon-neutral by 2035. But it has a major hurdle to overcome: Helsinki is one of the world’s coldest capital cities and currently uses coal to produce more than half of its heat, generating unacceptable quantities of carbon emissions. In addition to coal, the city relies on gas as well as biomass, the burning of which also adds to the city’s carbon emissions and impacts the country’s natural resources.
To highlight the scope of the challenge, we note that while the goal for the city is to be carbon-neutral by 2035, currently about 56% of Helsinki’s carbon emissions originate from the production of district heating. The volume and variation of its heat demand means it has been challenging to find a replacement for fossil fuels. And while other Nordic cities have opted to increase their use of biomass, Helsinki does not see that as a long-term sustainable solution.
In short, there is no ‘quick fix’ for the level of transition needed. Energy systems are complex and highly integrated, with multiple pieces of energy infrastructure interacting to produce and consume the energy that powers a city. While the public authorities and private sector acknowledge the need to start making sustainable changes soon, the solutions must be cost-effective, future-proof and acceptable to the local population. It is going to take innovation and the right private partners to deliver a sustainable transition.
District heating and cooling (DHC) is an efficient and well-established approach to providing thermal energy, yet it too faces numerous challenges. Potential users must meet certain conditions for DHC to be a viable solution: a varied distribution of offtakers in the same area, a sufficient volume of heat generated and a sufficient density of the various offtakers. A dense network of varied users enables the sharing of costs, thereby reducing the expense for each individual user.
District heating and cooling (DHC) is the centralized generation, storage and distribution of heating and cooling serving a range of consumers in a particular district, connected across a network of underground pipes and cables. With the increased use of renewable energy sources, however, generation is becoming more decentralized, blending into the urban landscape.
DHC is widely recognized as a sustainable, cost-effective solution to the provision of heating and cooling. The goal is now to increase the share of renewables across the various urban networks, providing comfort with space heating or conditioned air to everyone in commercial offices, community housing projects, industrial buildings and public facilities, while reducing CO2 emissions.
The real challenge beyond these general conditions, however, is how to build a DHC network that is cost-competitive, green and meets the high requirements of the City of Helsinki, with its cold climate and high-temperature network. What innovative solutions will be needed to deliver affordable, low-emissions energy without relying on biomass, thereby preserving natural resources? How to create new infrastructure while maintaining the value of the land? How to guarantee equitable deployment of the system and ensure the buy-in of the local population? In Helsinki’s case, we believe the answer lies in utilizing the city’s greatest natural resource: the Baltic Sea.
Major challenges like decarbonizing heat generation require innovation and the vision to harness its potential. The Helsinki story starts with the vision of forward-looking actors like the city’s mayor, who took a novel approach to encourage innovation. In 2020, he launched an international competition, the Helsinki Energy Challenge, to drastically and sustainably change the way the city generates its heat. The city offered one million euros in prize money for designing the best possible solution while using as little biomass as possible. In response to the mayor’s call, 252 teams from 35 countries submitted their ideas.
ENGIE Impact participated in the contest as a member of a European consortium of companies called HIVE, in which it was responsible for the energy mix. The group included ENGIE and its subsidiary Storengy (underground storage), Finnish solar collector manufacturer Savosolar, technical consultants from Newheat and PlanEnergi and the research institute AEE Intec. The proposal submitted by HIVE’s experts – given their experience in sustainability solutions, clean tech and environmental strategy – won the day.
HIVE’s winning solution is a master plan that would end the burning of coal by 2028, eliminate the need for fossil fuels by 2035 and reduce CO2 greenhouse gas emissions by 78% between 2020 and 2035.
Notably, this solution does not rely on the emergence of technological breakthroughs; rather, it utilizes the most advanced versions of proven, green technologies, organized in the most innovative way possible to deliver greater efficiency, better air quality and cheaper heat for end users.
Our proposed technical solution uses proven green technologies to produce heat by means of electricity. The primary source of this energy would be the sea, which accounts for 70% of the Helsinki area and is the obvious choice for a high-availability, low-emission, cost-competitive source. HIVE’s solution would deploy sufficient seawater heat pumps (SWHP) to give Helsinki the largest SWHP capacity in the world. It also expands capacity with the construction of two solar thermal fields, which would require modest land use and are already highly acceptable to the public. To address intermittency, the plan would additionally deploy electric boilers to address moments of peak capacity.
The truly innovative and most important element of this strategy concerns the introduction of low-temperature heating circuits across the network. Heat pumps work more efficiently at lower temperatures, so by reducing the temperature of the water going into the network, the entire system becomes more cost competitive.
Deploying two types of heat storage will lower the cost of energy and build resilience into the system, easing concerns about shortages during extreme cold spells or forced outages. High-capacity Borehole Thermal Energy Storage (BTES) is an innovative tactic of increasing energy storage capacity without impacting land values or creating an eyesore. Because they store heat underground (200-300m), minimizing their surface footprint, the boreholes can be placed in areas where land is of lower value or unsuitable for other purposes, such as unused space between road infrastructure. The land-use and visibility impacts are therefore negligible.
Pit Thermal Energy Storage (PTES) is a fast-response energy reservoir and a significant link in the proposed energy network, but it does raise concerns about land use, which raises the importance of fostering social acceptance and citizen engagement. For the fact of the matter is, even the most ingenious solution will never get off the ground without selling the approach to clients, stakeholders and the general public. Our proposal for Helsinki addresses this final piece of the puzzle extensively.
The plan addresses the concerns that clients and stakeholders might have about the initial costs and future profits involved in such a systematic, low-carbon overhaul of the city’s district heating. It demonstrates in detail how its innovative approaches to storage and demand-side management will lower the total cost of ownership. It also considers how to reduce total capital expenditure through grants and subsidies, given that the scale of emissions reductions generated by the project would make it an attractive applicant for various European funds.
Finally, it devises a plan to secure the engagement of the residents of Helsinki, whether by addressing their concerns about protecting natural ecosystems and resources, or by demonstrating the positive societal impacts that would result from its implementation: cleaner air, fewer greenhouse gasses and lower energy costs.
We consider our Helsinki proposal a “baseline scenario”, albeit a very ambitious one. It does not rely on the emergence of new technologies to realize its ambitions; rather, it is designed in such a way to be able to integrate them in the future.
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